The present invention relates to a plate exchange apparatus for a printing press, which exchanges an old plate gripped by plate lockup devices and mounted on the circumferential surface of a plate cylinder for a new plate prepared outside the apparatus.
A gap having a length almost equal to the overall length of a plate cylinder is formed in the circumferential surface of the plate cylinder for a printing press. A plate lockup apparatus consisting of a leading-side lockup device for gripping the leading end of a plate and a trailing-side lockup device for gripping the trailing end of the plate, the leading end of the plate being gripped by the leading-side lockup device while the plate is wound around the circumferential surface of the plate cylinder, is fixed on the bottom surface of the gap to extend in the axial direction of the plate cylinder. Each of the conventional leading- and trailing-side lockup devices comprises an elongated lockup table extending in the axial direction of the plate cylinder, a plurality of gripper plates, swingably supported at an edge portion of this lockup table by a plurality of bolts, for gripping or releasing the plate with or from the lockup table by being opened or closed as they swing, and a plurality of cams which can be respectively engaged with notches at the edges of the gripper plates. The plurality of cams are aligned along a pivotal cam shaft. A plurality of compression coil springs are interposed between the lockup table and the gripper plates to bias the gripper plates in an open direction.
With the above arrangement, in order to grip a plate, when the cam shaft is pivoted, the gripper plates are released upon disengagement from the cams and are opened by the elastic forces of the compression coil springs. An end of the plate is inserted between the gripper plates and the corresponding lockup table. When the cam shaft is pivoted in the direction opposite to the direction described above, the gripper plates are pivoted against the elastic forces of the compression coil springs by the behavior of the cams and closed, thereby gripping the end of the plate.
However, in the conventional plate lockup apparatus as described above, the cam shaft must be manually rotated in order to open and close the plate gripper surfaces, as described above. Therefore, the number of processing steps is increased to degrade the operability, resulting in need for much labor, and the preparation time is prolonged to degrade the operating efficiency of the printing press.
The present applicant developed and proposed a plate exchange apparatus in which a plate holding member holding a new plate is provided between units of the printing press, an old plate removed from the plate cylinder is discharged to and held in the plate holding member, and the new plate is discharged from the plate holding member and mounted on the plate cylinder. In this case, however, when the plate holding unit stores a plate, the lower half portion of the holding member is located at a position to cover a dampening arrangement of the printing unit. Thus, when maintenance/inspection of the dampening arrangement or replenishment of dampening water in a dampening water fountain is to be performed, the plate holding member interferes with the operation to degrade the operability and to cause a great danger. However, much labor is needed to manually remove the plate holding unit having a large weight from the maintenance work surface every time an inspection operation or the like is to be performed or to restore the plate holding unit to the initial position after the operation. Furthermore, since the plate holding unit having a precise arrangement must be moved with care, the operation requires a long period of time to prolong the preparation time, thus degrading the operating efficiency of the printing press.